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# What is the probability that a number selected from (-10, -6, -5, -4,

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What is the probability that a number selected from (-10, -6, -5, -4,  [#permalink]

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10 Jan 2017, 05:01
2
00:00

Difficulty:

45% (medium)

Question Stats:

62% (01:23) correct 38% (01:38) wrong based on 106 sessions

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What is the probability that a number selected from (-10, -6, -5, -4, -2.5, -1, 0, 2.5, 4, 6, 7, 10) can fulfill (x-5)(x+10)(2x-5)=0?
a) 1/12
b) 1/6
c) 1/4
d) 1/3
e) 1/2

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Anaira Mitch

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Re: What is the probability that a number selected from (-10, -6, -5, -4,  [#permalink]

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10 Jan 2017, 05:26
2
1
anairamitch1804 wrote:
What is the probability that a number selected from (-10, -6, -5, -4, -2.5, -1, 0, 2.5, 4, 6, 7, 10) can fulfill (x-5)(x+10)(2x-5)=0?
a) 1/12
b) 1/6
c) 1/4
d) 1/3
e) 1/2

-

(x-5)(x+10)(2x-5)=0 for x = 5, x = -10 or x = 5/2 = 2.5 (out of these 3 numbers only 2 are elements of the given set).

There are 12 numbers in the set thus the probability is 2/12 = 1/6.

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Re: What is the probability that a number selected from (-10, -6, -5, -4,  [#permalink]

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10 Jan 2017, 05:36
1
anairamitch1804 wrote:
What is the probability that a number selected from (-10, -6, -5, -4, -2.5, -1, 0, 2.5, 4, 6, 7, 10) can fulfill (x-5)(x+10)(2x-5)=0?
a) 1/12
b) 1/6
c) 1/4
d) 1/3
e) 1/2

-

Simplifying (x-5)(x+10)(2x-5)=0 for the values of x:
(x-5)=0 or (x+10)=0 or (2x-5)=0 ; x=5 or x=-10 or x=5/10=2.5

(-10, -6, -5, -4, -2.5, -1, 0, 2.5, 4, 6, 7, 10) >> 2 elements out of 12

Probability = 2/12 = 1/6

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Re: What is the probability that a number selected from (-10, -6, -5, -4,  [#permalink]

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10 Jan 2017, 19:21
First think: what can make the expression 0

the expression is (x-5)(x+10)(2x-5)

multiplication of 0 with any number results 0.

So if any of the term ((x-5),(x+10),(2x-5)) is 0, the result will be 0

i.e. to make the expression 0, the value of x should be 5 or -10 or 2.5

but the given set has only -10 or 2.5

so the favorable cases are 2

and total case=12

probability=2/12=1/6

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Re: What is the probability that a number selected from (-10, -6, -5, -4,  [#permalink]

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11 Jan 2017, 06:40
anairamitch1804 wrote:
What is the probability that a number selected from (-10, -6, -5, -4, -2.5, -1, 0, 2.5, 4, 6, 7, 10) can fulfill (x-5)(x+10)(2x-5)=0?
a) 1/12
b) 1/6
c) 1/4
d) 1/3
e) 1/2

Let’s first solve the given equation.

(x-5)(x+10)(2x-5) = 0

The values that satisfy the equation are x = 5, x = -10, or x = 5/2 = 2.5

Since only 2.5 and -10 are in the given list, the probability of selecting a number that fulfills the equation is 2/12 = 1/6.

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Re: What is the probability that a number selected from (-10, -6, -5, -4,  [#permalink]

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18 Apr 2018, 21:56
anairamitch1804 wrote:
What is the probability that a number selected from (-10, -6, -5, -4, -2.5, -1, 0, 2.5, 4, 6, 7, 10) can fulfill (x-5)(x+10)(2x-5)=0?
a) 1/12
b) 1/6
c) 1/4
d) 1/3
e) 1/2

-

This question very simple as commented by several people. But to me it is only difficult because this will catch you snoozing when you read through 5 from 4,6,7
Re: What is the probability that a number selected from (-10, -6, -5, -4, &nbs [#permalink] 18 Apr 2018, 21:56
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